mirror of
https://github.com/tailscale/tailscale.git
synced 2024-12-11 10:44:41 +00:00
82 lines
2.4 KiB
Go
82 lines
2.4 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// Package syncs contains additional sync types and functionality.
|
|
package syncs
|
|
|
|
import "sync/atomic"
|
|
|
|
// ClosedChan returns a channel that's already closed.
|
|
func ClosedChan() <-chan struct{} { return closedChan }
|
|
|
|
var closedChan = initClosedChan()
|
|
|
|
func initClosedChan() <-chan struct{} {
|
|
ch := make(chan struct{})
|
|
close(ch)
|
|
return ch
|
|
}
|
|
|
|
// WaitGroupChan is like a sync.WaitGroup, but has a chan that closes
|
|
// on completion that you can wait on. (This, you can only use the
|
|
// value once)
|
|
// Also, its zero value is not usable. Use the constructor.
|
|
type WaitGroupChan struct {
|
|
n int64 // atomic
|
|
done chan struct{} // closed on transition to zero
|
|
}
|
|
|
|
// NewWaitGroupChan returns a new single-use WaitGroupChan.
|
|
func NewWaitGroupChan() *WaitGroupChan {
|
|
return &WaitGroupChan{done: make(chan struct{})}
|
|
}
|
|
|
|
// DoneChan returns a channel that's closed on completion.
|
|
func (wg *WaitGroupChan) DoneChan() <-chan struct{} { return wg.done }
|
|
|
|
// Add adds delta, which may be negative, to the WaitGroupChan
|
|
// counter. If the counter becomes zero, all goroutines blocked on
|
|
// Wait or the Done chan are released. If the counter goes negative,
|
|
// Add panics.
|
|
//
|
|
// Note that calls with a positive delta that occur when the counter
|
|
// is zero must happen before a Wait. Calls with a negative delta, or
|
|
// calls with a positive delta that start when the counter is greater
|
|
// than zero, may happen at any time. Typically this means the calls
|
|
// to Add should execute before the statement creating the goroutine
|
|
// or other event to be waited for.
|
|
func (wg *WaitGroupChan) Add(delta int) {
|
|
n := atomic.AddInt64(&wg.n, int64(delta))
|
|
if n == 0 {
|
|
close(wg.done)
|
|
}
|
|
}
|
|
|
|
// Decr decrements the WaitGroup counter by one.
|
|
//
|
|
// (It is like sync.WaitGroup's Done method, but we don't use Done in
|
|
// this type, because it's ambiguous between Context.Done and
|
|
// WaitGroup.Done. So we use DoneChan and Decr instead.)
|
|
func (wg *WaitGroupChan) Decr() {
|
|
wg.Add(-1)
|
|
}
|
|
|
|
// Wait blocks until the WaitGroupChan counter is zero.
|
|
func (wg *WaitGroupChan) Wait() { <-wg.done }
|
|
|
|
// AtomicBool is an atomic boolean.
|
|
type AtomicBool int32
|
|
|
|
func (b *AtomicBool) Set(v bool) {
|
|
var n int32
|
|
if v {
|
|
n = 1
|
|
}
|
|
atomic.StoreInt32((*int32)(b), n)
|
|
}
|
|
|
|
func (b *AtomicBool) Get() bool {
|
|
return atomic.LoadInt32((*int32)(b)) != 0
|
|
}
|